In the drilling and completion industry, the formation of boreholes for the purpose of production or injection of fluid is common.
Packers are used in many applications downhole to accomplish a sealing function against an interior wall of well casing or borehole wall, such as to fill an annular space between a pipe string and the well casing wall or borehole wall or to receive tools therein such as packer plugs. Packer plugs are used to convert packers to temporary bridge plugs. When installed in the packer, the plug permits operations such as pressure testing, perforating, and washing above the packer without affecting the zone below the packer.
The internal diameter of the packer includes a thread for the packer plug to latch into. The thread is typically a left-hand square thread with 90 degree flank angles. The preferred method of inserting the plug into the packer top sub is with a downward push. That is because left hand rotation would be required to thread the plug into the top sub and that action could unscrew joints in the workstring. In deeper wells it becomes difficult to apply enough torque at the surface so that the sufficient releasing torque is applied at the engagement of the latched tool so that it will release. Thus, in order to insert the plug with a downward push and disengage the tool with an upward pull with no twist, the lead in flank angle of the tool is selected to promote ease of snapping into the square thread of the packer, such as 40 degrees, to seal in the packer bore. The back angle of the tool is selected to allow the latch to be pulled out of the packer, such as 30 degrees.
The art would be receptive to alternative devices for latching and releasing tools from packer bores and for increasing the ratings of latched tools used in packers.